Most microphones are designed to emulate the human ear, hearing sounds that we hear, and not hearing ones that we don't. Scientists from the University of Illinois at Urbana-Champaign, however, have created a new sound that we can't hear but that is picked up by mics of all kinds. It could have some valuable applications, although there's also the potential for misuse.
The university's Coordinated Science Laboratory states that the sound is produced by combining multiple tones that interact with a microphone's mechanical workings, creating what is known as a "shadow" – this is a type of white noise that is detectable only by the microphone, as it's formed within the mic itself.
Transmitted by ultrasonic speakers within a room, the sound could be used to keep confidential conversations from being clearly picked up by hidden listening devices. The people talking would still have no problem hearing each other, as the sound would be inaudible to them.
It could also thwart illegal audio recordings in movie theaters or music venues, plus it could be used in place of Bluetooth for wireless communication between Internet of Things (IoT) devices.
(Score: 3, Touché) by maxwell demon on Tuesday June 27 2017, @06:31PM (13 children)
Wouldn't it at the same time thwart the microphones of the musicians? I don't think the audience will enjoy it if there's only white noise coming from the speakers.
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by looorg on Tuesday June 27 2017, @06:51PM
I'm sure they'll invent some kind of blocking chip ... and then the pirates will install them into their cams and microphones to .. and then they'll have to invent some new anti-piracy thing ... and then ...
(Score: 2) by bob_super on Tuesday June 27 2017, @07:01PM
When will trolls get this in the same form factor as the TV-B-Gone?
(Score: 0) by Anonymous Coward on Tuesday June 27 2017, @07:17PM (2 children)
might not be an issue since the performer's mics are chosen and set not to pick up much of the surrounding noise of the concert, or feedback would be a big problem.
they could possibly keep this shadow noise from bleeding into those mics about as well as they keep the amplified sound from doing so.
(Score: 2) by http on Tuesday June 27 2017, @10:54PM
Sometimes the best mic for an instrument is omnidirectional. Feedback can be as much a function of the directionality of the monitors as of the microphones. And in case you haven't noticed, (i) feedback is a thing at live shows, and (ii) where it isn't a thing is where there's a highly experienced (and probably poorly paid) audio engineer on the main board.
I browse at -1 when I have mod points. It's unsettling.
(Score: 2) by Mykl on Wednesday June 28 2017, @12:11AM
Wouldn't this also be a potential solution to feedback as well then? If a microphone picks up too much of the speaker, it deadens the sound, preventing the feedback loop from taking place. The mic itself would only be silenced briefly before resuming normal operations.
Win-win?
(Score: 3, Insightful) by urza9814 on Tuesday June 27 2017, @07:18PM (1 child)
The sound is created in the microphone due to the physical construction of the device. So it might be possible to create special microphones which aren't susceptible. It may only be audible to most/all existing microphones because they share a fairly common and uniform shape and construction. Clearly there's *something* different about the human ear that is able to filter these out, so you should be able to replicate that somehow..even if it's just a matter of limiting the frequency response. Then instead of just an Arduino connected to a speaker, they can sell a whole kit with special microphones and everything too! And they'll have to charge a LOT for them to make sure the pirates can't afford to buy one -- corporate owners and security services only. ;)
(Score: 2) by kaszz on Wednesday June 28 2017, @01:59AM
To make a ear equivalent just manufacture a lot's of small tuning forks that can only sense one specific frequency and it's amplitude. This can be done using MEMS technique etc. All the signals from these will then be concatenated into one audio signal.
(Score: 3, Informative) by Osamabobama on Tuesday June 27 2017, @08:23PM
The obvious solution is to decouple the microphones from the speakers. If it is billed as a live show, the live nature could be simulated by unplugging the microphones. The performers would then act out the performance, taking cues from the pre-recorded sound being replayed through the speakers. (For proof of concept, see Justin Bieber, et al.)
Appended to the end of comments you post. Max: 120 chars.
(Score: 2) by driverless on Wednesday June 28 2017, @10:34AM (2 children)
Now all they need to deal with is the fact that blanketing a room with ultrasonics can do anything from giving people severe headaches to making them throw up by inducing intense nausea.
(Score: 2) by VLM on Wednesday June 28 2017, @11:36AM (1 child)
I can tell you with certainty that the marketing spin will be "you shouldn't be taking drugs at our concert venue". Victim blaming combined with refer madness.
(Score: 2) by driverless on Wednesday June 28 2017, @11:45AM
So you mean using a fake referrer URL to redirect traffic to your spam website which then gets blamed on the victim?
(Score: 2) by VLM on Wednesday June 28 2017, @11:30AM (1 child)
Reading between the lines they squeek out two ultrasonic tones and if they're loud enough (100 dB? 110 dB? 160 dB?), the mic can't handle it and instead of linear sampling two tones at 41KHz and 42KHz and the electronics tossing the noise out, the mechanic parts of the mic go nonlinear and you get signals at 41,42, and a mixed freq at 1 KHz ruining the recording.
Now an auto-notch filter can eat that 1 Khz signal but I just wanted easy math... you could broadcast two totally random frequencies that shift, or comically, shift with the music...
My gut level guess is to distort a mic takes enough ultrasound output to seriously injure people or at least cause freakouts for 50 miles among dogs.
Obviously some mic designs (of which many exist) are probably inherently low-pass and invulnerable.
(Score: 0) by Anonymous Coward on Wednesday June 28 2017, @12:55PM
Where are these figures from? I'd assumed wideband ultrasonic noise [soylentnews.org] between 25 and 40kHz which would (if loud enough) hit around the resonant frequency of the membrane and send the mic into self-oscillation. As you state, it's simply impossible to reproduce the ultrasonics loud enough to prevent a recording via this method without risking physiological effects and then it's trivial to reduce the audible effect on the microphone and post process the recording.
(Score: 2) by looorg on Tuesday June 27 2017, @06:40PM (3 children)
What about people with auditory-tactile synesthesia? Will they go nuts?
(Score: 0) by Anonymous Coward on Tuesday June 27 2017, @07:32PM
Naah. That kind of sound just feels a little mushy, sort of like oatmeal.
(Score: 3, Interesting) by VLM on Wednesday June 28 2017, @11:34AM
Hearing aids will be a bigger problem, especially with boomers and their $500 ticket retro concerts.
You tell a hippie to GTFO of a concert venue after he paid $5 in the 60s and he has a lifetime story about injustice from "the man". You tell him he can't enjoy his $500 or $1000 or whatever ticket for some reunion tour and there's gonna be lawyers and ...
Of course boomer reunion tour kind of implies anyone interested in hearing that stuff, heard that stuff 40 years ago and there can't be much sales loss so they might not bother. It might be more a teen-girl musician thing.
(Score: 2) by JoeMerchant on Wednesday June 28 2017, @12:27PM
In the 1970s/80s ultrasonic motion detectors for security systems were all the rage. Unfortunately, the designers apparently considered frequencies "above the perception threshold" of 99.9% of the human population to be adequately high - I could hear them, and they were painfully loud. I knew many people who could actually perceive them, though not as a painfully loud sound, but as a general discomfort vaguely associated with the ears. Funny thing about a shopping mall with 2000 shoppers in it, just by straight statistics: 99.9% doesn't include every person in the mall. If you want to go all civil rights on the thing, those systems were discriminating against people with acute high frequency hearing, denying them the opportunity for employment, and even denying them access to shop without having to wear some pretty serious hearing protection.
Same kind of problem applies to flashing screens on video games. Only 1% of the population has epilepsy, and only 1% of epileptics are "flash sensitive," that's a really small group, but it's still 1 per 10,000, and it includes somebody that a high-up in Sony management cares about, so we get those warnings before all the video games - which is probably appropriate since Sony has sold far more than 10,000 video game consoles.
🌻🌻 [google.com]
(Score: 2, Funny) by Anonymous Coward on Tuesday June 27 2017, @06:46PM (4 children)
Quick, into the cone of silence!
(Score: 0) by Anonymous Coward on Wednesday June 28 2017, @12:09AM (1 child)
What?
(Score: 0) by Anonymous Coward on Wednesday June 28 2017, @10:44AM
I SAID, INTO THE CONE OF SILENCE!
(Score: 2) by shortscreen on Wednesday June 28 2017, @12:26AM
Cone of silence is deprecated. Besides, this sounds more like hover-cover.
(Score: 0) by Anonymous Coward on Wednesday June 28 2017, @01:28PM
WHAT!?!
(Score: 2) by butthurt on Tuesday June 27 2017, @07:22PM
It isn't only microphones that can generate subharmonics/undertones in response to ultrasound. For example, the phenomenon happens in ultrasonic cleaners:
https://www.bjultrasonic.com/ultrasonic-cleaning-faqs/can-the-ultrasonic-sound-produced-by-ultrasonic-cleaners-damage-my-hearing/ [bjultrasonic.com]
I would guess that it's likely to happen in other objects which, unlike ultrasonic cleaners, aren't specifically designed to be around strong ultrasonic vibrations.
(Score: 0) by Anonymous Coward on Tuesday June 27 2017, @08:16PM (6 children)
Microphones can have various mesh designs and may use metal, foam and cloth to protect the transducer (diaphragm or ribbon). The resonance of the head basket varies between models and it does not take much mass to attenuate ultrasound frequencies. Either the ultrasound is played at an SPL where sub harmonics physically impede the functioning of the diaphragm or any louder audio frequencies would be somewhat recoverable from a recording.
(Score: 0) by Anonymous Coward on Tuesday June 27 2017, @08:53PM (3 children)
TFA is too vague, but I'd guess that this technique would have less effect the better quality microphone you use. Obviously studio mics with metallic mesh, foam batting and the nylon mesh screen might combat this phenomenon better than the little pinhole microphone on your cell phone or most portable recording devices. The intent seems to be to stop covert eavesdroppers. I think you'd spot the one with the boom-mic.
(Score: 1, Interesting) by Anonymous Coward on Tuesday June 27 2017, @09:50PM (2 children)
Great if you want to be blasting ultrasonic white noise at jet engine SPL (~120db) to have any chance of stopping someone recording a conversation. The interference caused by the ultrasonics has to be at least 9db louder than everything else in the recording to successfully mask it and it's trivial to effect a 12db reduction above 20kHz (17mm wavelength in air). I just took an SPL meter reading of myself talking in a small room, the meter pointed away from me and it was hitting 92db (C weighted). So it's not really a question of the microphone, just physics.
(Score: 0) by Anonymous Coward on Tuesday June 27 2017, @11:24PM (1 child)
Way to cherry pick one sentence, pull it out of context and use it as a straw man argument complete with buzzwords. I'll reiterate what I meant since it wasn't obvious. This technique will work on the microphones most often found in mobile and thus covert recording devices. you don't need ~120 db sound when any decent crosswind has the same effect as this sound emitter TFA talked about.
(Score: 1, Interesting) by Anonymous Coward on Wednesday June 28 2017, @09:12AM
Yes you do, as I have explained. 92dBC (SPL of my voice in a small room, meter pointed away) + 12dB (attenuation at 20kHz) + 9db (rule of thumb by which a louder sound will mask a sound at similar frequency) = 113dB. The recommended limit for prolonged exposure to ultrasonic frequencies in the UK is 115dB [hse.gov.uk] and the absorption coefficient of air at 20kHz yields roughly 0.5dB/M attenuation. Placing your "covert" recording device in a rolled up pair of socks will easily yield in excess of 3dB attenuation at 5kHz, 6dB at 10kHz and 12dB at 20kHz. What are you not understanding?
(Score: 2) by FatPhil on Wednesday June 28 2017, @03:46PM (1 child)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Wednesday June 28 2017, @09:47PM
How does the ultrasonic signal get to the LPF if it has *nothing* to do with the mechanical or acoustical properties of the mic? Mr Zobel long had the answer to the question of how to dampen filter ringing.
I have a frequency generator which is enough to feed breadboarded tests with RC filters or negative transformer feedback. It doesn't matter though, as I already wrote - we can acoustically LP ultrasound at wavelengths of 8.5mm before it even enters the mic chamber.
(Score: 2) by takyon on Tuesday June 27 2017, @08:38PM
Don't deprive us of our hot mic moments!
Top 10 Hot Mic Moments [time.com]
Hot mic catches DHS secretary joking about Trump attacking press with a saber [washingtonexaminer.com]
Trump goes after Obama again, cites 2012 hot mic conversation with then-Russian President Medvedev [latimes.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 0) by Anonymous Coward on Tuesday June 27 2017, @08:59PM (1 child)
This idea sounds like it came from a musician or a executive with no actual technical knowledge. It would be simple, maybe even trivial, to filter out the sound. Don't people remember the 2010 FIFA World Cup [wikipedia.org], and that annoying omnipresent din? It wasn't that hard to filter out that sound... would this be any harder? Maybe it couldn't be done real-time (yet... it would probably be easy to make software which could), but with a bit of post-production it wouldn't be that hard.
(Score: 2) by butthurt on Tuesday June 27 2017, @09:56PM
It might sound like this:
https://www.youtube.com/watch?v=YonDFAVtzKs [youtube.com]
(Score: 3, Funny) by rts008 on Wednesday June 28 2017, @02:25AM
While the new sound may insure privacy, an old sound I developed to a fine art guarantees privacy. It also peels paint, kills flies, and makes my eyes burn...but nothings perfect. ;-)
(Score: 0) by Anonymous Coward on Wednesday June 28 2017, @04:05AM
Worked in an office one time and the mgmt installed ultrasonic light switches, if no motion detected, then the lights turned off. Everyone got headaches, an engineer got a good sound level meter and discovered that the ultrasonics were at 120dB, sorry I don't remember the frequency, probably not too far outside the normal audible range. Shortly after, the management went back to trusting us to turn off the lights.